Merge branch 'master' into drift_on_demand

examples/main.c

@@ -45,6 +45,9 @@
 #define ENGINE_POLICY engine_policy_none
 #endif
 
+/* Global profiler. */
+struct profiler prof;
+
 /**
  * @brief Help messages for the command line parameters.
  */

src/Makefile.am

@@ -44,8 +44,7 @@ include_HEADERS = space.h runner.h queue.h task.h lock.h cell.h part.h const.h \
     common_io.h single_io.h multipole.h map.h tools.h partition.h clocks.h parser.h \
     physical_constants.h physical_constants_cgs.h potential.h version.h \
     hydro_properties.h riemann.h threadpool.h cooling.h cooling_struct.h sourceterms.h \
-    sourceterms_struct.h statistics.h memswap.h
-
+    sourceterms_struct.h statistics.h memswap.h profiler.h
 
 # Common source files
 AM_SOURCES = space.c runner.c queue.c task.c cell.c engine.c \
@@ -54,7 +53,7 @@ AM_SOURCES = space.c runner.c queue.c task.c cell.c engine.c \
     kernel_hydro.c tools.c part.c partition.c clocks.c parser.c \
     physical_constants.c potential.c hydro_properties.c \
     runner_doiact_fft.c threadpool.c cooling.c sourceterms.c \
-    statistics.c
+    statistics.c profiler.c
 
 # Include files for distribution, not installation.
 nobase_noinst_HEADERS = align.h approx_math.h atomic.h cycle.h error.h inline.h kernel_hydro.h kernel_gravity.h \

src/engine.c

@@ -59,6 +59,7 @@
 #include "parallel_io.h"
 #include "part.h"
 #include "partition.h"
+#include "profiler.h"
 #include "proxy.h"
 #include "runner.h"
 #include "serial_io.h"
@@ -322,6 +323,23 @@ void engine_redistribute(struct engine *e) {
                     MPI_COMM_WORLD) != MPI_SUCCESS)
     error("Failed to allreduce particle transfer counts.");
 
+  /* Report how many particles will be moved. */
+  if (e->verbose) {
+    if (e->nodeID == 0) {
+      size_t total = 0;
+      size_t unmoved = 0;
+      for (int p = 0, r = 0; p < nr_nodes; p++) {
+        for (int s = 0; s < nr_nodes; s++) {
+          total += counts[r];
+          if (p == s) unmoved += counts[r];
+          r++;
+        }
+      }
+      message("%ld of %ld (%.2f%%) of particles moved", total - unmoved, total,
+              100.0 * (double)(total - unmoved) / (double)total);
+    }
+  }
+
   /* Get all the g_counts from all the nodes. */
   if (MPI_Allreduce(MPI_IN_PLACE, g_counts, nr_nodes * nr_nodes, MPI_INT,
                     MPI_SUM, MPI_COMM_WORLD) != MPI_SUCCESS)

src/hydro/Minimal/hydro.h

@@ -66,7 +66,9 @@ __attribute__((always_inline)) INLINE static float hydro_get_internal_energy(
 __attribute__((always_inline)) INLINE static float hydro_get_pressure(
     const struct part *restrict p, float dt) {
 
-  return p->force.pressure;
+  const float u = p->u + p->u_dt * dt;
+
+  return gas_pressure_from_internal_energy(p->rho, u);
 }
 
 /**

src/partition.c

@@ -278,6 +278,18 @@ static void split_metis(struct space *s, int nregions, int *celllist) {
 #endif
 
 #if defined(WITH_MPI) && defined(HAVE_METIS)
+
+/* qsort support. */
+struct indexval {
+  int index;
+  int count;
+};
+static int indexvalcmp(const void *p1, const void *p2) {
+  const struct indexval *iv1 = (const struct indexval *)p1;
+  const struct indexval *iv2 = (const struct indexval *)p2;
+  return iv2->count - iv1->count;
+}
+
 /**
  * @brief Partition the given space into a number of connected regions.
  *
@@ -382,14 +394,70 @@ static void pick_metis(struct space *s, int nregions, int *vertexw, int *edgew,
     if (regionid[k] < 0 || regionid[k] >= nregions)
       error("Got bad nodeID %" PRIDX " for cell %i.", regionid[k], k);
 
+  /* We want a solution in which the current regions of the space are
+   * preserved when possible, to avoid unneccesary particle movement.
+   * So create a 2d-array of cells counts that are common to all pairs
+   * of old and new ranks. Each element of the array has a cell count and
+   * an unique index so we can sort into decreasing counts. */
+  int indmax = nregions * nregions;
+  struct indexval *ivs = malloc(sizeof(struct indexval) * indmax);
+  bzero(ivs, sizeof(struct indexval) * indmax);
+  for (int k = 0; k < ncells; k++) {
+    int index = regionid[k] + nregions * s->cells_top[k].nodeID;
+    ivs[index].count++;
+    ivs[index].index = index;
+  }
+  qsort(ivs, indmax, sizeof(struct indexval), indexvalcmp);
+
+  /* Go through the ivs using the largest counts first, these are the
+   * regions with the most cells in common, old partition to new. */
+  int *oldmap = malloc(sizeof(int) * nregions);
+  int *newmap = malloc(sizeof(int) * nregions);
+  for (int k = 0; k < nregions; k++) {
+    oldmap[k] = -1;
+    newmap[k] = -1;
+  }
+  for (int k = 0; k < indmax; k++) {
+
+    /* Stop when all regions with common cells have been considered. */
+    if (ivs[k].count == 0) break;
+
+    /* Store old and new IDs, if not already used. */
+    int oldregion = ivs[k].index / nregions;
+    int newregion = ivs[k].index - oldregion * nregions;
+    if (newmap[newregion] == -1 && oldmap[oldregion] == -1) {
+      newmap[newregion] = oldregion;
+      oldmap[oldregion] = newregion;
+    }
+  }
+
+  /* Handle any regions that did not get selected by picking an unused rank
+   * from oldmap and assigning to newmap. */
+  int spare = 0;
+  for (int k = 0; k < nregions; k++) {
+    if (newmap[k] == -1) {
+      for (int j = spare; j < nregions; j++) {
+        if (oldmap[j] == -1) {
+          newmap[k] = j;
+          oldmap[j] = j;
+          spare = j;
+          break;
+        }
+      }
+    }
+  }
+
   /* Set the cell list to the region index. */
   for (int k = 0; k < ncells; k++) {
-    celllist[k] = regionid[k];
+    celllist[k] = newmap[regionid[k]];
   }
 
   /* Clean up. */
   if (weights_v != NULL) free(weights_v);
   if (weights_e != NULL) free(weights_e);
+  free(ivs);
+  free(oldmap);
+  free(newmap);
   free(xadj);
   free(adjncy);
   free(regionid);

src/profiler.c

+/*******************************************************************************
+ * This file is part of SWIFT.
+ * Copyright (c) 2016 James S. Willis (james.s.willis@durham.ac.uk)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ ******************************************************************************/
+
+/* Config parameters. */
+#include "../config.h"
+
+/* Some standard headers. */
+#include <string.h>
+
+/* This object's header. */
+#include "profiler.h"
+
+/* Local includes */
+#include "clocks.h"
+#include "hydro.h"
+#include "version.h"
+
+/**
+ * @brief Resets all timers.
+ *
+ * @param profiler #profiler object that holds file pointers and
+ * function timers.
+ */
+void profiler_reset_timers(struct profiler *profiler) {
+
+  profiler->collect_timesteps_time = 0;
+  profiler->drift_time = 0;
+  profiler->rebuild_time = 0;
+  profiler->reweight_time = 0;
+  profiler->clear_waits_time = 0;
+  profiler->re_wait_time = 0;
+  profiler->enqueue_time = 0;
+  profiler->stats_time = 0;
+  profiler->launch_time = 0;
+  profiler->space_rebuild_time = 0;
+  profiler->engine_maketasks_time = 0;
+  profiler->engine_marktasks_time = 0;
+  profiler->space_regrid_time = 0;
+  profiler->space_parts_sort_time = 0;
+  profiler->space_split_time = 0;
+  profiler->space_parts_get_cell_id_time = 0;
+  profiler->space_count_parts_time = 0;
+}
+
+/**
+ * @brief Opens an output file and populates the header.
+ *
+ * @param e #engine object to get various properties.
+ * @param fileName name of file to be written to.
+ * @param functionName name of function that is being timed.
+ * @param file (return) pointer used to open output file.
+ */
+void profiler_write_timing_info_header(const struct engine *e, char *fileName,
+                                       char *functionName, FILE **file) {
+
+  /* Create the file name in the format: "fileName_(no. of threads)" */
+  char fullFileName[200] = "";
+  sprintf(fullFileName + strlen(fullFileName), "%s_%d.txt", fileName,
+          e->nr_nodes * e->nr_threads);
+
+  /* Open the file and write the header. */
+  *file = fopen(fullFileName, "w");
+  fprintf(*file,
+          "# Host: %s\n# Branch: %s\n# Revision: %s\n# Compiler: %s, "
+          "Version: %s \n# "
+          "Number of threads: %d\n# Number of MPI ranks: %d\n# Hydrodynamic "
+          "scheme: %s\n# Hydrodynamic kernel: %s\n# No. of neighbours: %.2f "
+          "+/- %.2f\n# Eta: %f\n"
+          "# %6s %14s %14s %10s %10s %16s [%s]\n",
+          hostname(), functionName, git_revision(), compiler_name(),
+          compiler_version(), e->nr_threads, e->nr_nodes, SPH_IMPLEMENTATION,
+          kernel_name, e->hydro_properties->target_neighbours,
+          e->hydro_properties->delta_neighbours,
+          e->hydro_properties->eta_neighbours, "Step", "Time", "Time-step",
+          "Updates", "g-Updates", "Wall-clock time", clocks_getunit());
+
+  fflush(*file);
+}
+
+/**
+ * @brief Writes the headers for all output files. Should be called once at the
+ * start of the simulation, it could be called in engine_init() for example.
+ *
+ * @param e #engine object to get various properties.
+ * @param profiler #profiler object that holds file pointers and
+ * function timers.
+ */
+void profiler_write_all_timing_info_headers(const struct engine *e,
+                                            struct profiler *profiler) {
+
+  profiler_write_timing_info_header(e, "enginecollecttimesteps",
+                                    "engine_collect_timesteps",
+                                    &profiler->file_engine_collect_timesteps);
+  profiler_write_timing_info_header(e, "enginedrift", "engine_drift",
+                                    &profiler->file_engine_drift);
+  profiler_write_timing_info_header(e, "enginerebuild", "engine_rebuild",
+                                    &profiler->file_engine_rebuild);
+  profiler_write_timing_info_header(e, "schedulerreweight",
+                                    "scheduler_reweight",
+                                    &profiler->file_scheduler_reweight);
+  profiler_write_timing_info_header(e, "schedulerclearwaits",
+                                    "scheduler_clear_waits",
+                                    &profiler->file_scheduler_clear_waits);
+  profiler_write_timing_info_header(e, "schedulerrewait", "scheduler_rewait",
+                                    &profiler->file_scheduler_re_wait);
+  profiler_write_timing_info_header(e, "schedulerenqueue", "scheduler_enqueue",
+                                    &profiler->file_scheduler_enqueue);
+  profiler_write_timing_info_header(e, "engineprintstats", "engine_print_stats",
+                                    &profiler->file_engine_stats);
+  profiler_write_timing_info_header(e, "enginelaunch", "engine_launch",
+                                    &profiler->file_engine_launch);
+  profiler_write_timing_info_header(e, "spacerebuild", "space_rebuild",
+                                    &profiler->file_space_rebuild);
+  profiler_write_timing_info_header(e, "enginemaketasks", "engine_maketasks",
+                                    &profiler->file_engine_maketasks);
+  profiler_write_timing_info_header(e, "enginemarktasks", "engine_marktasks",
+                                    &profiler->file_engine_marktasks);
+  profiler_write_timing_info_header(e, "spaceregrid", "space_regrid",
+                                    &profiler->file_space_regrid);
+  profiler_write_timing_info_header(e, "spacepartssort", "space_parts_sort",
+                                    &profiler->file_space_parts_sort);
+  profiler_write_timing_info_header(e, "spacesplit", "space_split",
+                                    &profiler->file_space_split);
+  profiler_write_timing_info_header(e, "spacegetcellid", "space_get_cell_id",
+                                    &profiler->file_space_parts_get_cell_id);
+  profiler_write_timing_info_header(e, "spacecountparts", "space_count_parts",
+                                    &profiler->file_space_count_parts);
+}
+
+/**
+ * @brief Writes timing info to the output file.
+ *
+ * @param e #engine object to get various properties.
+ * @param time Time in ticks to be written to the output file.
+ * @param file pointer used to open output file.
+ */
+void profiler_write_timing_info(const struct engine *e, ticks time,
+                                FILE *file) {
+
+  fprintf(file, "  %6d %14e %14e %10zu %10zu %21.3f\n", e->step, e->time,
+          e->timeStep, e->updates, e->g_updates, clocks_from_ticks(time));
+  fflush(file);
+}
+
+/**
+ * @brief Writes timing info to all output files. Should be called at the end of
+ * every time step, in engine_step() for example.
+ *
+ * @param e #engine object to get various properties.
+ * @param profiler #profiler object that holds file pointers and
+ * function timers.
+ */
+void profiler_write_all_timing_info(const struct engine *e,
+                                    struct profiler *profiler) {
+
+  profiler_write_timing_info(e, profiler->drift_time,
+                             profiler->file_engine_drift);
+  profiler_write_timing_info(e, profiler->rebuild_time,
+                             profiler->file_engine_rebuild);
+  profiler_write_timing_info(e, profiler->reweight_time,
+                             profiler->file_scheduler_reweight);
+  profiler_write_timing_info(e, profiler->clear_waits_time,
+                             profiler->file_scheduler_clear_waits);
+  profiler_write_timing_info(e, profiler->re_wait_time,
+                             profiler->file_scheduler_re_wait);
+  profiler_write_timing_info(e, profiler->enqueue_time,
+                             profiler->file_scheduler_enqueue);
+  profiler_write_timing_info(e, profiler->stats_time,
+                             profiler->file_engine_stats);
+  profiler_write_timing_info(e, profiler->launch_time,
+                             profiler->file_engine_launch);
+  profiler_write_timing_info(e, profiler->space_rebuild_time,
+                             profiler->file_space_rebuild);
+  profiler_write_timing_info(e, profiler->engine_maketasks_time,
+                             profiler->file_engine_maketasks);
+  profiler_write_timing_info(e, profiler->engine_marktasks_time,
+                             profiler->file_engine_marktasks);
+  profiler_write_timing_info(e, profiler->space_regrid_time,
+                             profiler->file_space_regrid);
+  profiler_write_timing_info(e, profiler->space_parts_sort_time,
+                             profiler->file_space_parts_sort);
+  profiler_write_timing_info(e, profiler->space_split_time,
+                             profiler->file_space_split);
+  profiler_write_timing_info(e, profiler->space_parts_get_cell_id_time,
+                             profiler->file_space_parts_get_cell_id);
+  profiler_write_timing_info(e, profiler->space_count_parts_time,
+                             profiler->file_space_count_parts);
+
+  /* Reset timers. */
+  profiler_reset_timers(profiler);
+}
+
+/**
+ * @brief Closes all output files, should be called at the end of the
+ * simulation.
+ *
+ * @param profiler #profiler object that holds file pointers and
+ * function timers.
+ */
+void profiler_close_files(struct profiler *profiler) {
+
+  fclose(profiler->file_engine_drift);
+  fclose(profiler->file_engine_rebuild);
+  fclose(profiler->file_scheduler_reweight);
+  fclose(profiler->file_scheduler_clear_waits);
+  fclose(profiler->file_scheduler_re_wait);
+  fclose(profiler->file_scheduler_enqueue);
+  fclose(profiler->file_engine_stats);
+  fclose(profiler->file_engine_launch);
+  fclose(profiler->file_space_rebuild);
+  fclose(profiler->file_engine_maketasks);
+  fclose(profiler->file_engine_marktasks);
+  fclose(profiler->file_space_regrid);
+  fclose(profiler->file_space_parts_sort);
+  fclose(profiler->file_space_split);
+  fclose(profiler->file_space_parts_get_cell_id);
+  fclose(profiler->file_space_count_parts);
+}

src/profiler.h

+/*******************************************************************************
+ * This file is part of SWIFT.
+ * Copyright (c) 2016 James S. Willis (james.s.willis@durham.ac.uk)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ ******************************************************************************/
+#ifndef SWIFT_PROFILER_H
+#define SWIFT_PROFILER_H
+
+/* Config parameters. */
+#include "../config.h"
+
+/* Local includes */
+#include "engine.h"
+
+/* Profiler that holds file pointers and time taken in functions. */
+struct profiler {
+
+  /* File pointers for timing info. */
+  FILE *file_engine_collect_timesteps;
+  FILE *file_engine_drift;
+  FILE *file_engine_rebuild;
+  FILE *file_scheduler_reweight;
+  FILE *file_scheduler_clear_waits;
+  FILE *file_scheduler_re_wait;
+  FILE *file_scheduler_enqueue;
+  FILE *file_engine_stats;
+  FILE *file_engine_launch;
+  FILE *file_space_rebuild;
+  FILE *file_engine_maketasks;
+  FILE *file_engine_marktasks;
+  FILE *file_space_regrid;
+  FILE *file_space_parts_sort;
+  FILE *file_space_split;
+  FILE *file_space_parts_get_cell_id;
+  FILE *file_space_count_parts;
+
+  /* Time taken in functions. */
+  ticks collect_timesteps_time;
+  ticks drift_time;
+  ticks rebuild_time;
+  ticks reweight_time;
+  ticks clear_waits_time;
+  ticks re_wait_time;
+  ticks enqueue_time;
+  ticks stats_time;
+  ticks launch_time;
+  ticks space_rebuild_time;
+  ticks engine_maketasks_time;
+  ticks engine_marktasks_time;
+  ticks space_regrid_time;
+  ticks space_parts_sort_time;
+  ticks space_split_time;
+  ticks space_parts_get_cell_id_time;
+  ticks space_count_parts_time;
+};
+
+/* Function prototypes. */
+void profiler_reset_timers(struct profiler *profiler);
+void profiler_write_all_timing_info_headers(const struct engine *e,
+                                            struct profiler *profiler);
+void profiler_write_all_timing_info(const struct engine *e,
+                                    struct profiler *profiler);
+void profiler_close_files(struct profiler *profiler);
+
+#endif /* SWIFT_PROFILER_H */

src/space.c

@@ -173,18 +173,69 @@ int space_getsid(struct space *s, struct cell **ci, struct cell **cj,
  *
  * @param s The #space.
  * @param c The #cell to recycle.
+ * @param rec_begin Pointer to the start of the list of cells to recycle.
+ * @param rec_end Pointer to the end of the list of cells to recycle.
  */
-void space_rebuild_recycle(struct space *s, struct cell *c) {
-
+void space_rebuild_recycle_rec(struct space *s, struct cell *c,
+                               struct cell **rec_begin, struct cell **rec_end) {
   if (c->split)
     for (int k = 0; k < 8; k++)
       if (c->progeny[k] != NULL) {
-        space_rebuild_recycle(s, c->progeny[k]);
-        space_recycle(s, c->progeny[k]);
+        space_rebuild_recycle_rec(s, c->progeny[k], rec_begin, rec_end);
+        c->progeny[k]->next = *rec_begin;
+        *rec_begin = c->progeny[k];
+        if (*rec_end == NULL) *rec_end = *rec_begin;
         c->progeny[k] = NULL;
       }
 }
 
+void space_rebuild_recycle_mapper(void *map_data, int num_elements,
+                                  void *extra_data) {
+
+  struct space *s = (struct space *)extra_data;
+  struct cell *cells = (struct cell *)map_data;
+
+  for (int k = 0; k < num_elements; k++) {
+    struct cell *c = &cells[k];
+    struct cell *rec_begin = NULL, *rec_end = NULL;
+    space_rebuild_recycle_rec(s, c, &rec_begin, &rec_end);
+    if (rec_begin != NULL) space_recycle_list(s, rec_begin, rec_end);
+    c->sorts = NULL;
+    c->nr_tasks = 0;
+    c->density = NULL;
+    c->gradient = NULL;
+    c->force = NULL;
+    c->grav = NULL;
+    c->dx_max = 0.0f;
+    c->sorted = 0;
+    c->count = 0;
+    c->gcount = 0;
+    c->init = NULL;
+    c->extra_ghost = NULL;
+    c->ghost = NULL;
+    c->kick = NULL;
+    c->drift = NULL;
+    c->cooling = NULL;
+    c->sourceterms = NULL;
+    c->super = c;
+    if (c->sort != NULL) {
+      free(c->sort);
+      c->sort = NULL;
+    }
+#if WITH_MPI
+    c->recv_xv = NULL;
+    c->recv_rho = NULL;
+    c->recv_gradient = NULL;
+    c->recv_ti = NULL;
+
+    c->send_xv = NULL;
+    c->send_rho = NULL;
+    c->send_gradient = NULL;
+    c->send_ti = NULL;
+#endif
+  }
+}
+
 /**
  * @brief Re-build the top-level cell grid.
  *
@@ -303,10 +354,8 @@ void space_regrid(struct space *s, int verbose) {
 
     /* Free the old cells, if they were allocated. */
     if (s->cells_top != NULL) {
-      for (int k = 0; k < s->nr_cells; k++) {
-        space_rebuild_recycle(s, &s->cells_top[k]);
-        if (s->cells_top[k].sort != NULL) free(s->cells_top[k].sort);
-      }
+      threadpool_map(&s->e->threadpool, space_rebuild_recycle_mapper,
+                     s->cells_top, s->nr_cells, sizeof(struct cell), 100, s);
       free(s->cells_top);
       s->maxdepth = 0;
     }
@@ -394,44 +443,12 @@ void space_regrid(struct space *s, int verbose) {
     // message( "rebuilding upper-level cells took %.3f %s." ,
     // clocks_from_ticks(double)(getticks() - tic), clocks_getunit());
 
-  } /* re-build upper-level cells? */
-
+  }      /* re-build upper-level cells? */
   else { /* Otherwise, just clean up the cells. */
 
     /* Free the old cells, if they were allocated. */
-    for (int k = 0; k < s->nr_cells; k++) {
-      space_rebuild_recycle(s, &s->cells_top[k]);
-      s->cells_top[k].sorts = NULL;
-      s->cells_top[k].nr_tasks = 0;
-      s->cells_top[k].density = NULL;
-      s->cells_top[k].gradient = NULL;
-      s->cells_top[k].force = NULL;
-      s->cells_top[k].grav = NULL;
-      s->cells_top[k].dx_max = 0.0f;
-      s->cells_top[k].sorted = 0;
-      s->cells_top[k].count = 0;
-      s->cells_top[k].gcount = 0;
-      s->cells_top[k].init = NULL;
-      s->cells_top[k].extra_ghost = NULL;
-      s->cells_top[k].ghost = NULL;
-      s->cells_top[k].kick = NULL;
-      s->cells_top[k].drift = NULL;
-      s->cells_top[k].cooling = NULL;
-      s->cells_top[k].sourceterms = NULL;
-      s->cells_top[k].super = &s->cells_top[k];
-      s->cells_top[k].ti_old = 0;
-#if WITH_MPI
-      s->cells_top[k].recv_xv = NULL;
-      s->cells_top[k].recv_rho = NULL;
-      s->cells_top[k].recv_gradient = NULL;
-      s->cells_top[k].recv_ti = NULL;
-
-      s->cells_top[k].send_xv = NULL;
-      s->cells_top[k].send_rho = NULL;
-      s->cells_top[k].send_gradient = NULL;
-      s->cells_top[k].send_ti = NULL;
-#endif
-    }
+    threadpool_map(&s->e->threadpool, space_rebuild_recycle_mapper,
+                   s->cells_top, s->nr_cells, sizeof(struct cell), 100, s);
     s->maxdepth = 0;
   }
 
@@ -1616,24 +1633,22 @@ void space_split_mapper(void *map_data, int num_cells, void *extra_data) {
 }
 
 /**
- * @brief Return a used cell to the buffer od unused sub-cells.
+ * @brief Return a used cell to the buffer of unused sub-cells.
  *
  * @param s The #space.